Understanding hypoxia and time of useful consciousness, and altitude-related psyiology? Sure.

Understanding the nuances of oxygen systems, if he's not flying an aircraft with them installed, or capable of going to higher altitudes, or capable of being pressurized? That line of questioning is not required, and is not appropriate.

Tell me, young skywalker, how do the outflow valves operate, at what altitude do they drive closed, what powers them and what's the failure mode for that actuator and that power source, and what's the backup? Now explain overpressurization. Tell me about those negative pressure relief valves in your Cessna 172, and by the by, demonstrate and explain, and better yet draw the damn thing out, your aerox quick-donning mask.

It's a wonder this examiner didn't demand proof that the kid did a session in an altitude chamber.

Odd that the FAA uses an endorsement for all that, should the intrepid aviator eventually seek flight in high-altitude equipment. Go figure.

The commercial is a glorified private pilot. I did my commercial long cross country in an airplane without radios and no electrical system. I was not expected to man the space shuttle. At such time as young skywalker gets tasked with turbine airplanes and pressurized vessels, he will be instructed in the nuances thereof.

The difference between the experienced aviator, and the novice? The novice is heard to say, "what's that thing doing?" while the seasoned flight vet observes, "hey, that thing's doing it again."